The present invention is directed toward rotating electric machines having slip rings and an air circulation fan.
An alternator design popular among automotive manufacturers incorporates a pair of internal air circulating fans. One such design manufactured by General Motors Corporation through Delphi Automotive Systems is shown in cross section in FIG. 1 hereof. Alternator 10 has a rotor assembly generally designated by the reference numeral 20 and stator assembly generally designated by the reference numeral 15. The rotor assembly 20 includes a shaft 21 supporting all rotating magnetic circuit structures thereof including conventional pole-members 16A and 16B, rotor core 17 and field coil 18 wound upon bobbin 12. Additionally, all other non-magnetic circuit rotating structures are carried thereby, including air circulation fans 19 and 27 located at axially opposite sides of the pole-members, and a slip ring assembly 30 located at one extreme end of the shaft. Fan 27 is formed from sheet metal stock and spot welded to pole-member 16B while fan 19 is formed from an appropriate thermoplastic material and heat staked to tower extensions (not shown) from the field coil bobbin 12. The shaft 21 in turn is rotatably supported within a housing 26 by a pair of bearings 23 and 22. Bearing 23 is located between the slip ring assembly 30 and the fan 19.
Coil leads 18A of field coil 18 are wrapped about respective posts 12A of bobbin 12 and pass through holes 13 in fan 19. Slip ring assembly 30 is made of a pair of copper rings 31, each having a slip ring lead 32 joined such as by welding thereto. The copper rings and wires are molded into a thermoset material to complete the slip ring assembly. Slip ring assembly 30 is pressed onto the end of rotor shaft 21 and the slip ring leads 32 are routed into channels along the shaft 21 where they are joined such as by twisting and welding to the coil leads 18A of field coil 18. The joint 24 is then bent to the surface of the fan 19 and typically secured thereto such as by heatstaking. Bearing 23 is assembled to pass over the slip ring assembly 30 to retain the lead wires 32 securely within the shaft channels.